Barnes & Noble shareholder G Asset Management offered to buy 51 percent of its college bookstore business in a deal valuing the unit at $460 million as the company considers options to boost its value.

Divesting the chain of 641 college bookstores would unlock more value for Barnes & Noble, which is “substantially undervalued,” New York-based G Asset Management said in a letter addressed to the company’s board.

Barnes & Noble, the largest bookstore chain in the US, has been considering separating its Nook digital unit into a separate company so investors will give it the higher valuation of a technology business.

The company’s shares gained 2.3 percent last year after a 26-percent drop in 2010.

G Asset said the cash and equity portion of the purchase price may come from additional investors and that it intends to discuss the proposal with other Barnes & Noble shareholders. The college unit would assume $410 million of company debt in the proposed deal, the fund said.